JPH04210409A - Production of fine metal or alloy powder - Google Patents

Abstract

PURPOSE:To produce fine metal powder made uniform in size in large quantities at a low cost by jetting fluid from plural nozzles in the form of sheets so that the sheets intersect each other and feeding a molten metal to a long cross region along the intersection in the form of a film. CONSTITUTION:Gas, liq. or other fluid jetted at a high flow rate is collided against a flow of a molten metal or alloy to obtain fine metal or alloy powder. In this atomizing method, the fluid 12 is jetted from plural nozzles in the form of sheets so that the sheets intersect each other and the molten metal or alloy 10 as starting material is fed to a long cross region along the intersection 18 in the form of a sheet so that this sheet is allowed to coincide with the intersection 18. In order to feed the molten metal 10 in the form of a sheet, a molten metal nozzle is made rectangular and magnetism is preferably allowed to act on the flow of the molten metal by arranging electromagnets around a feed pipe. Fine spherical metal or alloy powder of about 10-20mum particle size can be efficiently and stably obtd.

Description

[Detailed description of the invention]

[00011

[Industrial Application Field] The present invention is directed to so-called atomization, in which a stream of metal or alloy material in a high-temperature molten state is made to collide with a high-velocity jet of gas or liquid to atomize the metal or alloy material to obtain fine powder. Concerning improvements in methods. [0002] Injection molding using fine metal powder requires a fine and clean spherical powder with a particle size of about 10 to 201I11, which has good fluidity and sinterability. [0003] Furthermore, it has been found that in many cases materials that are prone to segregation and have poor workability when manufacturing products by melting and casting can be molded satisfactorily by using powder metallurgy. [0004] Conventionally, there have been the following methods for producing powders required in these fields. [0005] In the atomization method, high-temperature molten metal material is made to flow down in the form of a rod or sheet, and a high-velocity fluid is injected and collided with it at a certain angle, thereby making the molten metal fine and cooling it. This is a method that can produce metal powder in large quantities. Depending on the type of fluid used, this method is sometimes called a gas atomization method or a liquid atomization method. [0006] Another method is to use a gas whose solubility in the molten metal material is significantly different between the liquid phase state and the solid phase state.
Specifically, there is a method of dissolving a large amount of hydrogen, carbon oxide, or nitrogen in a liquid phase and blowing it up into a tank at room temperature, or atomizing it and pulverizing the metal material by releasing gas. Are known. [0007] As an improved method of these, JP-A-2-198
No. 620 describes that a plurality of flows of melt to be atomized are supplied into an inverted conical film-like fluid flow and atomized. This technique reduces the amount of steam generated at the grinding site by dispersing the melt flow instead of concentrating it in one location, and also allows the steam to be carried away downward. [0008]

[Problem to be solved by the invention] However, the particle size of 10~
Fine and clean metal spherical powders of about 20 μm or less, especially clean fine powders of alloys, have poor industrial yields and are therefore very expensive. [0009] Also in the case of powder metallurgy, although the raw material powder needs to be fine, it has conventionally been difficult to supply powder materials that are industrially profitable. [00101Furthermore, when attempting to obtain fine powder by gas atomization or liquid atomization, fluid is injected at high speed and large flow rate, but the fluid injection causes an upward fluid flow, making the molten metal flow unstable. Problems have arisen in that the molten metal material cannot be effectively atomized, or that the molten metal material adheres to and blocks the fluid injection nozzle. [00111] In the above-mentioned known technology, the melt flow is divided in order to disperse the large amount of steam generated in the atomized part, but the melt flow is divided by passing it through a large number of thin nozzles. Therefore, the nozzle is easily clogged, which poses a problem in reliably producing fine powder.

[001-2] The object of the present invention is to eliminate the problems in the known techniques described above and to provide a method for obtaining fine powder of a metal or alloy material in large quantities at low cost by an atomization method. [0013] [Means for Solving the Problems] In order to achieve the above-mentioned object, the inventor of the present invention has conducted extensive research and found that both the molten fluid stream to be pulverized and the jetted fluid stream are brought into contact in the form of a sheet. The present inventors have found that this is effective in refining and sizing the obtained powder, and have completed the present invention. [0014] That is, the present invention uses the atomization method,
In producing metal or alloy powder, the flow of jetting fluid that atomizes the flow of molten metal material is jetted from a plurality of jetting holes preferably located at symmetrical positions so that the flow of jetting fluid intersects in a sheet shape, and the sheet-like jetting The present invention relates to a method for producing fine powder, which comprises supplying the molten metal material, previously formed into a sheet, to an elongated intersection region of fluids. [0015] Further, according to the present invention, in order to form the molten metal flow into a sheet shape, an electromagnet is arranged around a molten metal pipe that is a molten metal material supply pipe, and a magnetic field is applied to change the shape of the molten metal into a sheet shape. A more effective method is to produce a fine powder by jetting it out in a sheet-like manner in a controlled manner and pulverizing it with jet fluids that intersect with each other. [0016]

[Operation] The structure and operation of the present invention will be explained. The production of fine powder according to the present invention is basically an atomization method. [001,7] When producing fine alloy powder by the atomization method, the smaller the size of the raw material molten metal (for example, the diameter of the molten metal flow), the smaller the diameter of the generated powder. Regarding the average particle size of powder produced by the atomization method, the experimental formula reported by Lubanska fits well, but according to this relational expression, the powder particle size decreases in proportion to the square root of the diameter of the molten metal flow. [0018] In addition, as a method of reducing the diameter of the molten metal while improving the productivity of powder and simultaneously preventing solidification and clogging in the nozzle due to the temperature of the molten metal, it is possible to form the molten metal into a sheet and combine it with a plurality of jetting fluids. It is suitable to inject the injection fluid so that the lines of intersection of the two coincide with each other. In order to make the molten metal flow down in a sheet shape, it is not enough to make the molten metal outlet rectangular because the surface tension of the molten metal is large, so magnetic force is used in combination to form the molten metal flow into a sheet shape by the magnetic field action of a magnet. It is effective to do so. [00191 The present invention utilizes the atomization method, and as shown in the concept in FIG. The elongated intersection area shown by line 18 is fed. [00201 In a cylindrical molten metal stream flowing down from a commonly used nozzle, the action of the injection fluid is different between the surface and the inside, and the injection fluid does not act much on the inside of the molten metal flow, making it difficult for the molten metal flow to deform. Relatively coarse particles are produced, resulting in a low yield of the desired fine powder and a wide distribution of powder particle size ranges. In contrast, according to the present invention, by supplying the molten metal flow in the form of a sheet, the jetting fluid that deforms and splits the molten metal acts uniformly on the entire molten metal. The width of the sheet-shaped molten metal is preferably slightly narrower than the sheet-shaped width of the jetting fluid, but there is no particular restriction as long as it can be sufficiently atomized by the jetting fluid. Here, a slit nozzle may be used as the nozzle shape for the molten metal, but if the slit width is too narrow, there is a risk of clogging problems as in the case of a thin tube, so for example, the nozzle shape may be a hole type.
It may also be formed into a sheet by utilizing the so-called pinch effect of electromagnets provided around it. [00213] Furthermore, the injection holes for ejecting the injection fluid in the form of a sheet are arranged symmetrically, and the medium is ejected in the form of a sheet from each of the pair of injection holes to collide on a certain intersection line to form an intersection area. By supplying the molten metal flowing down in the form of a sheet onto the long intersection line of this intersection area, the deformation and splitting action of the jet fluid on the molten metal becomes strong and uniform, producing fine powder and sized powder. be able to. Examples of the nozzle shape for blowing out the jetting fluid in the form of a sheet include a slit nozzle, a nozzle in which a large number of fine holes are arranged in a line, and the like. [0022] FIG. 2 shows the atomization method in which the jetted fluid has an inverted conical shape ((1)) disclosed in Japanese Patent Publication No. 52-19181 and the like, and the vertical cross section of the jetted fluid film used in the method of the present invention is V. Regarding the atomization method ((2)) that results in a letter shape,
The flow velocity distribution was measured under the same conditions at the position where the injected fluid collides with the molten metal, that is, the intersection area referred to in the present invention. As a result, it can be seen that the V-shaped injection fluid has a much flatter flow velocity distribution, and the force of the injection fluid acting on the molten metal becomes uniform, which is advantageous for producing sized powder. [0023]

EXAMPLE The present invention will be explained based on an example using the apparatus shown in FIG. FIG. 3 is a schematic diagram of a powder manufacturing apparatus using the gas atomization method. In FIG. 3, 37 is a powder recovery tank, and a vacuum chamber 31 is installed in the upper part of the powder recovery tank 37, and inside the vacuum chamber 31, an atomizer is supplied with injection fluid from a high-pressure gas pipe 36 to a connection part with the powder recovery tank. A nozzle 35 is installed. Molten metal material container 3 installed above the center of the atomizing nozzle 35
2 is provided with a molten metal pipe 34 for injecting molten metal into the atomizing nozzle 35. Through this molten metal pipe 34, the molten metal material 33 is supplied to the atomizing nozzle 35, and the molten metal material 33 is supplied to the atomizing nozzle 35. The molten metal atomized by the fluid jetted from 36 becomes powder and is collected in the powder recovery tank 37 . 38 is a cyclone separator. The analytical values of the chemical components of the molten metal used in this example are as shown in Table 1. [0024]

[Table 1] [0025]

[Example 1] Molten metal having the chemical components shown in Table 1 was atomized under the conditions shown in Table 2 using the shape and dimensions (mu) of the outlet of the molten metal nozzle shown in FIG. The results of measuring the particle size distribution are shown in FIG. The injection shape of the injection fluid is V-shaped, and the width dimension of the intersection area is 20
It was mm. [0026]

[Table 2] [0027] For comparison, particle dust distribution of powder generated under the same conditions in Table 2 using the shape and dimensions (mm) of the molten metal pipe, that is, the molten metal outlet shown in FIG. is also shown in FIG. The injection shape and conditions of the injection fluid were the same as in the method of the present invention described above. From the results shown in FIG. 6, it is clear that the method of the present invention is more effective in producing fine powder with uniform particle size than the conventional method. When the fluidity is expressed as a fluidity index, it is 12.5 for the method of the present invention and 14. for the conventional method.
8, indicating that the powder produced by the method of the present invention has excellent fluidity. [0028] Furthermore, even if the shape of the molten metal pipe outlet is rectangular, the surface tension of the molten metal is generally high, so the molten metal flow is deformed into a cylindrical shape. Further, generally, making the shape of the outlet of the molten metal pipe rectangular has problems in that the strength of the refractory is reduced due to the formation of a thin walled portion, and that it is difficult to form the refractory into a shape with a large aspect ratio. [0029]

[Embodiment 2] In this example, as shown in FIG. 7, an electromagnetic coil is installed around the molten metal flow flowing out from a molten metal pipe having a circular molten metal outlet whose shape and dimensions are shown in FIG. was set up to form a magnetic field. In FIG. 7, an electromagnet 70 is installed so as to sandwich the molten metal pipe 34, while the ejected fluid 12
passes through the supply pipe 72 and is sprayed in the form of a sheet from a nozzle. The molten metal flow flowing down from the molten metal pipe 34 has a cylindrical shape immediately after leaving the nozzle, but is formed into a sheet shape by the magnetic action of the electromagnet 70 before colliding with the injection fluid. When the maximum applied magnetic flux density at the center of the magnetic rod was set to 2.1 Tesla using the illustrated apparatus, it was observed that the molten metal flow was deformed into a flat plate shape. Powder was produced under the conditions shown in Table 2, and the particle size distribution of the produced powder is shown in FIG. From this result, it was proved that it is possible to achieve finer powder size and particle size regulation by providing an electromagnetic coil to form a magnetic field and causing the molten metal to flow down in a sheet shape. The conventional method in the figure was the same as that of Example 1. The fluidity index of the powder produced by the above method was 11.8, which was almost the same as that when the molten metal nozzle of FIG. 4 was used. [00301] [Effects of the Invention] Since the present invention is configured as explained above, it has the effect of being able to produce fine and sized metal or alloy powder at low cost and in large quantities by the atomization method. , is extremely useful in industry.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of the production of fine powder by spraying sea 1 underflow upper molten metal with a V-shaped jet fluid according to the present invention.

FIG. 2 (1) is an explanatory diagram of the flow velocity distribution of the injection fluid at the position where the injection fluid collides with the molten metal. FIG. 2(2) is an explanatory diagram of the flow velocity distribution of the injection fluid at the position where the injection fluid collides with the molten metal.

FIG. 3 is a schematic diagram of a powder manufacturing apparatus using the gas atomization method of the present invention.

FIG. 4 is a schematic view showing the shape and dimensions of the outlet of the sheet-like dissolving enteric tube of the present invention.

FIG. 5 is a schematic diagram showing the shape and dimensions of a conventional circular hole-shaped molten metal pipe outlet.

FIG. 6 is a graph showing the results of measuring the particle size distribution of atomized powder.

FIG. 7 is a conceptual diagram of the atomization method of the present invention that combines sheet-like flow of molten metal by an electromagnetic coil.

8 is a graph showing the particle size distribution measurement results of the atomized powder and the conventional example using the apparatus of FIG. 7. FIG.

[Explanation of symbols]

31 Vacuum chamber 32 Molten metal tundish 33 Molten metal A Molten metal pipe 35 Atomize nozzle 36 High pressure gas piping 37 Atomize tank 38 Cyclone separator

[Figure 3]

Claims (2)

[Claims] [Claim 1] When manufacturing metal or alloy powder by the atomization method, a plurality of jets of the jet fluid that atomizes the molten metal material flow are arranged in pairs so that the jet fluid flows intersect in a sheet shape. A method for producing fine metal or alloy powder, characterized in that the molten metal material is injected from a hole and the molten metal material is previously formed into a sheet shape and supplied to a long intersection area of the flow of the jetted fluid. 2. The method for producing fine metal or alloy powder according to claim 1, wherein the molten metal material flow is previously formed into a sheet shape by the magnetic action of an electromagnet disposed around the molten metal material supply pipe.